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Fat Shots on '09 Ultra Classic, where to start?

I just ordered a set of Supertrapp Fat Shots (model #728-71576) for my 2009 Harley-Davidson Ultra Classic. The bike has a Stage 1 upgrade and I'm replacing a set of high performance mufflers that are just too loud for me. I'm wondering how many discs to start with when I first install them. I want it to be as quiet as possible without hurting the performance I've paid for in my Stage 1 upgrade. I think the installation instructions recommend starting with 10 discs, but the '09 Touring bikes (non-California) did not have a catalytic converter in their stock headers, so that tends to make them a little louder than the '10 and up models. That makes me think 8 or 9 discs might be a better starting point, but I'm hoping to get some guidance from someone with experience in that area. Thanks in advance for the help!

Flow wise, even as few as 6 discs you will still be outflowing the stock mufflers by about 10%.
However, even with 10-12 discs, those are still very quiet mufflers. Your thought of 8-9 would be fine.
Be sure to use all of the supplied anti-seize grease in the threads of the muffler bodies, use the entire package.
Thank you.

Originally Posted by Calvin1989

I just ordered a set of Supertrapp Fat Shots (model #728-71576) for my 2009 Harley-Davidson Ultra Classic. The bike has a Stage 1 upgrade and I'm replacing a set of high performance mufflers that are just too loud for me. I'm wondering how many discs to start with when I first install them. I want it to be as quiet as possible without hurting the performance I've paid for in my Stage 1 upgrade. I think the installation instructions recommend starting with 10 discs, but the '09 Touring bikes (non-California) did not have a catalytic converter in their stock headers, so that tends to make them a little louder than the '10 and up models. That makes me think 8 or 9 discs might be a better starting point, but I'm hoping to get some guidance from someone with experience in that area. Thanks in advance for the help!

I wanted to follow up on this, in case anyone else is doing an installation on a bike with a similar set up. I decided to start with 10 discs to see how loud they would be. I've only done a short ride so far (about 30 minutes), but the sound is exactly what I was looking for. It has all the nice deep low tones without the droning or "blat" that I've had with other performance exhausts I've tried. It's very quiet at cruising speed (maybe even quieter than the stock mufflers). In fact, it's quiet enough that I could probably run all 12 discs, but I think I'll quit while I'm ahead. For now, I'm very happy with the Fat Shots.